Duplex control circuit



1o, v1944s.

DUPLEX zcoNTRoL CIRCUITx Filed July 24, 1944 IN VEN TOR.

Patented Sept. 10, 1946 2,407,399` y DUPLEX CONTROL CIRCUIT l Robert vW. Carlson, VDepew, and -Madison G. Nicholson, Jr., Snyder, N. Y., assignors to vColonial Radio Corporation, Buialo, N. Y.v

Application July 24, l1944, Serial No. 546,404

L 15 Claims. 1

This invention relates to duplex Control circuits, and more particularly to such circuits as may be employed to control a transmitter which may operate with one of a number of different characteristics; that is to say, the transmitter may be controlled from two different keying positions I and 2 and each of the keying positions may controla number of different modulators, each having its `own particular characteristicy which it impresses onthe carrier.'

For instance, in keying position I there may be, for example, four different modulators A, B, C, and D. Modulator A may, for example, cause the transmitter to send two pulses of predetermined length with a predetermined spacing between them. Modulator B may cause the transmitter to send three pulses of predetermined length and spacing, modulator C- four pulse-s of predetermined length and spacing, andmodulator D five pulses of predetermined length and spacing, and any yone of these may be operated from its particular switch or key in keying position I. f

Keying position 2 may'similarly control four modulators', such as E, F, G, and I-I., E may'cause the transmitter to send two' pulses of predeter-` mined lengthwith a predetermined'spacing be# .tween them, and these pulse and space lengths may be different from those of the modulators in keying position I. Similarlymodulators F, G, and H may cause the transmitter to send 3, Il, and 5 pulses` of predetermined length and spacing diiTering from the length and spacing of the pulses controlled b-y modulators A, B, C, and D.

It is to be understood that the action of the modulators is not repeated; that is to say, if L the key controlling modulator A be closed in keying position I, the transmitter willr send two pulses separated by a space of predetermined length, and no further action will occur unless the key is opened and closed again, at which time the transmitter" will again send ltwo pulses with a predetermined space between them.

This action, as will be understood, is analogous to that of a'magnetically operated bell which has no interrupter in its circuit so that when the .L

switch is closed, the bell will strike only once and not ring continuously. Furthermore, the transmission is completed in a few milliseconds so that it is possible for a modulator in keying position 2 to follow very rapidly the action of a modulator in keying position I.

It is desired to provide a control circuit which will permit operation of any modulator at will, as maybe desired, but it is also'imlportant to prevent blocking of the modulators or improper or faulty operation which might occur provided the control keys for the modulators in positionA I and position 2 were operated simultaneously. Since only one modulator can be permitted to operate at a time on the transmitter, it is nec-esvAt the same time, to prevent one modulator bei ing rendered. inoperative, it is desirable tto provide control circuits whereby these modulatorszmay be alternately operable in turn for a period ofl time which isgsuflicient to permit them tofsend out` the desired signal. n

For example, in the operation of `our control circuit, supposinglthat a key in keying position I and another key in keying position 2 yare closed simultaneously. Then, under such conditions, one key will operate its modulator to send out the signal characteristic of the operating modulator, and after this action is completed, control is transf-erred to thel other modulator, which causes the transmitter to send out a signal modulated with the characteristic of the other modulator, and the entire process of operation may be completed in lan extremely short period of time; for example, of 'the order of 1/1oo` ofa'second.

Thus, while the two modulators act successively arid never simultaneously in point of time, yet

their operations follow eachother so quickly that invention described and claimed in the coi-pending' application of Madison G. Nicholson, Jr., entitled Duplex control circuit, owned by the assignee of the present application.

It is an object of this invention to provide an improved duplex control circuit which will prevent one modulator from controlling the transmitter While the other is in control.

It is a, further object of this invention to provide such a circuit in which the operation of the second modulator, although temporarily prevented .from occurring While the first modulator is in control of the transmitter, will, nevertheless, occur within an extremely short interval of time after the control key is operated. VIt is still a further -o'oect of our invention to provide an improved control circuit for applying two modulators to a transmitter alternately for very short periods of time whereby in effect duplex operation is provided.

AIt is still a further object `of our invention to provide such a control circuit in which more than two modulators may be employed, the first being any one of a group of modulators which may be selectively employed and the second being any one of another group of modulators which may be selectively employed. Y

Still other objects and advantages of our invention will be apparent from the specification.

The features of novelty which We believe to be vcharacteristic of our invention are set forth with partcularty in the appended claims. Our invention itself, however, both as to its 4fundamental principles' and as nto its., particular embodiments, will best be understood'by reference tothe specification and accompanying drawing, in which The single figure is a circuit diagram of an improved duplex control system in accordance with" our invention.

Referring now more particularly to the drawing, it indicates the transmitter, which may be controlled by any one of the modulators A, B, C, or D in keying position i, and by any one of the modulators E, E', G, and lin keying position 2. The construction and operation of the modulators is not shown or described in detail since these form per se no part of this invention.

Modulators A, B, or C may be selected and put into operation by means of switches 3l, 39, and 4i respectively in keying position I and any one of modulators E, F, and G may be selected and put into operation by switches 38, sil, and i2 in keying position 2 respectively. Modulator D in keying position I and modulator H in` keying |position 2 are not provided with a selecting switch since these send clearing signals at theV completion of operation of any other modulator of the same keying position and are caused to operate by the circuits herein employed, as will be described Prevention of operation oa modulator oi position I simultaneously with the modulator of position 2 is prevented by a pair of tubes which may be of the thyratron type I I and I2, tube II having cathode IIc, control grid IIg, screen grid IIeg. and anode I Ia. Similarly tube I2 may have cathode I2C, control grid 12g, screen grid I zsg, and

anode I2a. l

In the embodiment of the invention herein shown, the cathodes of these tubes are connected to ground through resistances I S and I4, and the plate circuit of tube I I is connected to one end of the actuating winding of relays 2S, 3|, k33. and 35 in keying position I. The other end of the winding of relay 29 is connected to front contact 31j of switch 3l', winding of relay 3.I to front contact 39j of switch 39, and the other terminal of the winding of relay 33 to front contact 4 if of switch fil. The other terminal of' relay winding 35 is connected to back contact Mb of switch 4I, the blade of switch 4! connected to back contact 3% of switch 39, and the blade of switch 39 connected to back contact 31h of switch 31 and through resistance 43 to the source of supply -I.- B.

Switches 31, 39. and Il are preferably springbiased to back contact position, and they are of the type in which there is no wipe-over; that is to say, when they are moved from back contact to front contact position, there is an intermediate position in which the switch is open, relay 29 controls its contacts 29e, relay 3! its contacts 3 Ic, relay 33 its contacts ttc, and relay 35 its Contacts 35e, these contacts beinor normally biased to open position and closed by the flow of current through their respective windings.

Contacts 29e close the circuit controlling modulator A. contacts 3io modulator Bi, contacts 33C modulator C, and contacts 35e modulator D, in such a manner that when any one of these relays operates, its respective modulator is put in control of the transmitter and causes the transmission of the signal characteristic of such modulator, Keying position 2 is entirely similar to keying position I.

Anode I2a of tube 2&2 is connected to onerend of the actuating windings of relays 3Q, 32, 34, and 36, the other end of which may be connected to front contact 38j cfgswitch 38, the other end of winding 4. of relay 32 to fromu contact 40j of switch et, the other end of the winding of relay Sel to front contact fs2f of switch t2, Vand the other end of the winding or relay St to back contact ith of switch 42.

Like switches 3l', 3S, and 4i, switches 38, 135i, and t2 may be biased to back contact position, and are arranged so that there is an interval of time when the circuitl is open as the switch is moved from back contact to front contact. The blade of switch i2 is connected to the back contact of switch til, the blade of switch lli) to the back contact of switch 35, and the blade of switch 3B through resistance it to the -I- B source.

Contacts Etc of relay 3@ close the circuit to modulator E, contacts 32e to modulator F, contacts 32o to modulator G, and contacts `tic to modulator H. The -I- B source is connected through resistance l5 to the cathode of tube Ii and through resistance it to the cathode of tube I2.

For controlling tubes I! and I2, we provide a multivibrator comprising tubes 2i and 22, the -former having cathode 2SC, control electrode Zig, and anode i2 la, and thev latter cathode 22e, control electrode 22g, and anode 22a,

y'lhe cathodes of tubes 2l and 22 are connected together and to ground, the grids through resistances 23 and fi respectively to the -I- B supply, and resistance 23 is shunted by condenser 25 to resistance 2l in series, and resistance 2l! shunted by condenser 26 and resistance 28 in series.

The intermediate point of resistance 2l and condenser 25 is connected through a differentiating network comprising condense-r i9 and resistance I'I to grid llg of vtube I l, and the intermediate point of condenser 2S and resistance 28 similarly connected through a differentiating network comprising condenser 2li and resistance i3 to grid lg of tube I2. Anode 25a of tube 2I is connected to the intermediate point between condenser 25 and resistance 2&3 and anode 22a of tube 22 to the intermediate point between` condenser ?!5 and resistance 2l.

The constants of this multivibrator circuit are preferably so chosen that the circuit delivers a square wave having a frequency of the order of 25 cycles per second. Consequently, there will be applied to grid Mn of tube ll through the differentiating network condenser I5? and resistance II 25 positive pulses per second and te grid 12g of tube 4I2 through differentiating network condenser 12!) and resistance I8 25 positive pulses per second, and these will be delivered alternately, rst to tube I l, then to tube I2, so that these grids electrically may be regarded as the opposite ends of a see-saw, never going positive at the same time.

Of course, negative 'pulses are also applied to said grids once per cycle. but since these negative pulses play no part in the operation of the circuit, they need not be considered.

The operation will now be described with reference to keying position l, and it will be understood that the description as applied to keying position I applies equally to keying position 2. Under normal conditions; that is, when no signal is being transmitted, the relays and switches are in the position shown. Tube I! is ionized and will remainY ionized, the negative pulse which is periodically impressed upon this tube by the multivibrator being insufficient to deionize.

Plate current flows only through the winding of relay 35, and contacts 35e are closed. The contacts of the other relays, 29, 3i, and 33, are

g open, and the plate circuit of tube II is completed through back contact Mb, blade of switch 4I, back contact 39h, bladev of switch 39, back7 contact 3Ib, and blade of switch 3l.

If now switch 4| be moved from back to front contact, the plate circuit of tube-II is open during the interval when'the blade of switch 4I moves off back contact 4Ib until it reaches front contact 4If. By opening the plate circuit, tube 3l is caused to deionize, this interrupting plate current through relay and allowing relay contacts 35o to open.

When the blade of switchVlII reaches front contact, the plate circuit oftube II is completed through the winding of relay 33. The operating voltages on tube II are so chosen that the tube will not ionize until a positive pulse is impressed upon grid' I Ig from the multivibrator. Therefore, tube II will remain in deionized condition until a positive pulse reaches grid IIg. When this occurs, tube I I ionizes and plate current beginsv to flow through winding of relay 33, thereby energizing the relay and causing closure of contacts33c, and the closure of these contacts Vcauses operation of modulator C, causingrthe transmitter to send the characteristic signal produced by modulator C.

Once the signal has been sent, no further action will occur so long as switch III is held on front contact 4If. When this switch is released,

it is carried back to bac-k contact, and in passing off front contact 4U opens the plate circuit of tube II, which causes deionization of the tube. 'Il'n's interrupts the plate current flowing through the actuating winding of relay 33 and contacts 33o open. As soon as switch 4I closes on back contact, the plate circuit of the tube is again completed, `but the tube does not reionize until the next positive pulse from the multivibrator is impressed upon its grid. f

When this occurs, the tube fires and the plate current flowing through the winding of relay 35 closes contacts 35o, and molulator D isestablished as the controlling molulator, causing the transmitter to send the clearing signal. completes the cycle of'operation, and the apparatus is now ready for another closure of switches 31, 3S, or 4I to front contact. y it will be understood that operation of the modulator in keying position` 2 is the same as that already described except'toat they are controlled by tube I2 instead -of tube II and that, as already stated, no modulator of keying position I can operate while any modulator of keying position 2 is operating, and vice versa.

Suppose, now, that switch 4| in keying position I and switch 42 in keying' position 2 happen to be closed simultaneously. It cannot be predicted which tube, II or I2, will ionize rst, this being dependent upon which rst receives the positive pulse from the multivibrator. If it happens that tube I2 receives the positive pulse before tube II, then tube I2 will first ionize and modulator G will be put in control, sending out its characteristic group of pulses.

If switch 4I is still closed after the signal is sent by modulator G, fthen the contacts of relay 33 will be closed, modulator C of position I will beI placed in control, and its characteristic signal will be sent. Upon release of keys 4I and 42 modulators D and I-I will be successively established in control and both clearing signals sent, depending on which of tubes II and I2 first receives a positive pulse.

Thus, it will be seen'that if a switch in keying This position I and a switch in keying positionV 2v are simultaneously closed for about 1/25 second or longer, four signals will be sent; rst', the operating signal from either keying position I or 2, depending upon which of tubes II and I2 is rst ionized; second, the operating signal from the other-keying position; third, the clearing signal from the one keying position; and finally, the

clearing signal from the other keying position; and the entire sequence of operation will be completed in not more than a tenth of a second longer than theV time during which the keys were held down.

While we have shown and describedvcertain preferred embodiments of our invention, it will be understood that modications and changes may be made without departing from the spirit .and scope thereof, as will be clear to those skilled in the art.

In this application we have particularly pointed out andhdistinctly claimed the part, improvement, or combination Which we claim'as our invention or discovery,l and we have explained the principles thereof and the best mode in which we have contemplated applying those principles so as tc distinguish our invention from other inventions.

We claim:

l. The combination with a transmitter, of a plurality of banks'of modulators, each bank comprising a plurality of modulators, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each modulator respectively, and means for causing sequential operation of the modulators when two switches controlling molulators in different banks are closed simultaneously.

2.l The combination with a transmitter, of a yplurality of banks of modulators, each bank comprisingV a plurality of modulators, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each modulator respectively, means ,for causing sequential operation of a modulatorY in each bank kwhen their control switches are closed simultaneously, said last mentioned means includingv a pair of gas discharge tubes, and means for preventing simultaneous ionization of said tubes.

3. The combination with a transmitter, of a plurality' of banks of modulators, each bank comprising a plurality of modulators, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each modulator respectively, means for causing sequential operation of a modulator in each of said banks when their controlling switches are closed simultaneously, said last mentioned means includinga pair of gas discharge tubes, means for preventing simultaneous ionization of said tubes, and a relay for each modulator respectively operated by the space current of said gaseous discharge tubes.

4. The combination with a transmitter, of a plurality of banks of modulators, each bank co-mprising a plurality of modulators, each arranged tc impress its characteristic modulation on the transmitter, aswitch for controlling each of said modulators respectively, means for causing'sequential operation of one modulator in each bank when their control switches are closed simultaneously, said last mentioned means including a pair of gas discharge tubes each having a control electrode, a substantially square wave generator,

means forV impressing alternately upon said control electrodes positive pulses derived from the output of said square Wave generator.

5. 'Ehe combination with a transmitter, of a plurality of banks of modulators, each bank comprising a plurality 0l modulators, each arranged to impress its characteristic modulation on .the transmitter, a switch for controlling each modulator respectively, means for causing sequential operation ci one modulator in each bank when their control switches are closed simultaneous said last mentioned means including a pair of gas discharge tubes each having a control electrode, a generator of substantially square waves, and a pair of diierentiating net works connected to said electrodes respectively and to points oi 160 degrees phase opposition in said square wave generator.

The combination with a transmitter, of a plurality of banks or modulators, each bank com prising a plurality of modulators, each arranged to impress its characteristic modulation on the transmitter, switches for controlling said modi;n laters respectively, means for causing sequential operation of one modulator in each bank when their controlling switches are closed simultaneously, said last mentioned means including a pair ci gas discharge tubes each having a pair of control electrodes, a generator of substantial square waves, means for applying alternately positive pulses from said square wave generator to one or said control electrodes in each tube, the other of said control electrodes being normally biased with respect to the cathode of its respective tube so as to prei/ent ionization thereof, said switches being arranged to alter the bias on said last mem tioned control electrode in the respective tubes to a valve such that the tube will ionize when a positive pulse applied to the other control electrode of said tube.

7. In a signaling system, in combination, a transmitter, a plurality of modulators, each pressing a predetermined characteristic upon the transmitted signal, and a switch for selectively operating each of said modulators, said switches having front and back contact positions, and being interconnected in a manner such that when all of said switches are on back Contact position a control circuit is established.

3. In a. signaling system, in combination, a transmitter, a plurality of working signal modulators and a clearing signal modulator and `a switch for controlling each of said working modulators, said switches having front and back contact positions and being so connected that when all of said switches are on back contact position the control circuit is closed for operating said clearing modulator.

9. In a signaling system, in combination, a transmitter, a plurality of working signal modulators, and a clearing signal modulator, a thyratron, a relay ior each modulator having one terminal of its energizing winding connected in the anode circuit of said thyratron, and a switch for each of said working signal modulators for completing the circuit through the respective energizing winding, said switches having front and back contacts and being so interconnected that when the said switches are on back contact position the circuit through the energizing winding of the clearing signal modulator relay is completed.

l0. In a signaling system, in combination, a transmitter, a plurality of working signal modulators, and a clearing signal modulator, each impressing a predetermined characteristic upon the transmitted signal,V means for selectively causing operation of any one ,of said working signal modulators, and means for energizing the clearing signal modulator at the completion of the working modulator signal.

11. In a signaling system, in combination, a transmitter, a plurality of working signal modulators, and a clearing signal modulator, means for selectively energizing any one of said working signal modulators, said means operating to interrupt the control circuit of said clearing signal modulator whenever the control circuit of any working modulator is established.

12. In a signaling system, in combination, a transmitter, a plurality of working signal modulators, and a clearing signal modulator, and means for selectively operating any one of said working signal modulators, said means operating, when actuated, to interrupt the control circuit oi said clearing signal modulator and establishing the control circuit of said clearing signal modulator when returned to initial position.

13. The combination with a transmitter, of a plurality oi banks of modulators, each bank comprising a plurality of working signal modulators and a clearing signal modulator, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each Working signal modulator respectively, means for causing sequential operation of one f-.rorking signal modulator of each bank when two working modulator signal switches in diiierent banks are closed simultaneously, the switches in each bank being so interconnected that the closure of a working signal modulator contro-l switch in either bank interrupts the controlv circuit to the clearing modulator of said bank.

14. The combination .with a transmitter, of a plurality of ba ci modulators, each bank com* prising a plurality of worl g signal modulators and a clearing signal modulator, each arranged to impress its c' ai yoteristic modulation on the transmitter, a switch for controlling each working signal modulator respectively, means for causing sequential operation of a working signal modulator in each bank when their control switches are closed simultaneously, said last mentioned means including a pair of gas discharge tubes, and means for preventing simultaneous ionization of said tubes, the switches o each bank being interconnected so that when all of the switches oi either bank are in bank contact position the control circuit to the clearing modulator of said bank is established.

l5. The combination with Va transmitter, of a plurality of banks of modulators, each bank oomprising a plurality of working signal modulators and a clearing signal modulator, each arranged to impress its characteristic modulation on the transmitter, a switch for controlling each working signal modulator respectively, means for causing sequential operation of a modulator in each of said banks when their respective controlling circuits are closed simultaneously, said last mentioned means including a pair of gas discharge tubes, means for preventing simultane ous ionization of said tubes, and a relay for each modulator respectively, operated b-y the space current of said gaseous discharge tubes, the switches of each bank being interconnected in a manner to establish the control circuit t0 the clearing signal modulator of said bank when all of the switches in said bank are on back contact.

ROBERT W. CARLSON. Y MADISON G. NICHOLSON, JR. 

